Interspecific Scaling and Ontogenetic Growth Patterns of the Skull in Living and Fossil Ctenomyid and Octodontid rodents (Caviomorpha: Octodontoidea).

VASSALLO ALDO IVÁN; MORA MATÍAS SEBASTIÁN

The Quintessential Naturalist: Honoring the Life and Legacy of Oliver P. Pearson.

University of California Press (Berkely-Los Angeles-London)

Lugar: Davis (California); Año: 2007; p. 945 - 968

We assessed the effect of size on skull attributes of ctenomyid and octodontid rodent species using an allometric approach. We focus on traits which have long been considered of relevance for tooth digging, such as the development of the mandibular angle and masseteric crest, and the robustness of incisors. Interspecific comparisons of adult specimens revealed important shape differences between Ctenomys, on one hand, and octodontid genera (except Spalacopus and, partly, Aconaemys) plus the early ctenomyid Actenomys, on the other. In addition, we found that larger Ctenomys species possess both proportionally broader lower jaws and more robust incisors. For these traits, the ontogenetic trajectories of the skull in the small Ctenomys talarum and large C. australis do not differ in either slope (allometric coefficient) or intercept. In this sense, our study clearly shows that evolutionary ontogenetic scaling was associated with skull shape variation within the limits of a single genus, Ctenomys. On the other hand, C. australis and the extinct Actenomys, which differ sharply in skull morphology and possibly in fossorial habits and ecological niche, differ significantly in the slope and/or intercept of their ontogenetic trajectories. This fact indicates the complexity of changes in development responsible for the departure from ontogenetic scaling in ancient and extant ctenomyines, in association with morphological diversification of the skull above the species level. Key words: allometry, Ctenomys, ontogeny, Rodentia, skull